1. Field of the Invention
The invention relates to a radio communication apparatus used for both digital communications and analog communications.
2. Description of the Prior Art
FIG. 3 shows a block diagram of a conventional radio communication apparatus. In FIG. 3, a microphone 1 changes human voice to voice signal. A linear codec 3 converts the voice signal to a digital signal. A digital signal processor (DSP) 4 processes the digital signal. A ROM 52 stores instruction codes (voice coding procedures) used in the DSP 4. A digital modulation/demodulation portion 6 modulates the coded digital signal to form the modulated digital signal and demodulates the modulated signal to form the coded digital signal.
An analog voice signal processing portion 12 modulates the voice signal to form the modulated voice signal and demodulates the modulated voice signal to form the voice signal. An FM modulation/demodulation portion 10 modulates the modulated voice signal to form the FM signal and demodulates the FM signal to form the modulated voice signal. A radio frequency transmitter/receiver 7 amplifies the signals which are received from the modulation/demodulation portion 6 or FM modulation/demodulation portion 10 and sends them to an antenna 8, and receives radio frequency signal from the antenna 8 and sends them to digital modulation/demodulation portion 6 or the FM modulation/demodulation portion 10. A speaker 2 converts the voice signal which is received from linear codec 3 or analog voice signal processing portion 12 to the voice and outputs the voice. A control portion 11 controls the devices in the radio communication apparatus.
The operation of the above conventional art is explained hereinafter.
(1) In the case of voice signal processed in a digital manner.
Firstly, the voice which is input to the microphone 1 is converted to an analog signal and is sent to a linear codec 3. The linear codec 3 converts the analog voice signal which is received from the microphone 1 to the digital signal and outputs it to the DSP 4. The DSP 4 processes the digital signal which is received from the linear codec 3 according to the voice coding procedure which is stored in the ROM 52 and sends the coded signal to the digital modulation/demodulation portion 6. The digital modulation/demodulation portion 6 modulates the carrier signal by the coded signal and outputs the digital modulated signal to the radio frequency transmitter/receiver 7. The radio transmitter/receiver 7 amplifies the received digital modulated signal and sends it to the base station via the antenna 8.
When the radio frequency signal are received from the base station via the antenna 8, the radio frequency transmitter/receiver 7 sends the radio signal to the digital modulation/demodulation portion 6. The digital modulation/demodulation portion 6 demodulates the digital modulated signal and outputs the demodulated signal to the DSP 4. The DSP 4 decodes the demodulated signal according to the signal procedure stored in the ROM 52 and sends the decoded digital voice signal to the linear codec 3. The linear codec 3 converts the digital voice signal to the analog voice signal and sends it to the speaker 2. The speaker 2 converts the analog voice signal to voice output.
(2) In the case of voice signal processed in an analog manner.
Firstly, the voice which is input in the microphone 1 is converted to an analog signal and is sent to an analog voice signal processing portion 12. The analog voice signal processing portion 12 modulates the analog signal to the modulation voice signal for FM transmission and sends it to the FM modulation/demodulation portion 10. The FM modulation/demodulation portion 10 modulates the carrier signal by the modulation voice signal and outputs the modulated FM signal to the radio frequency transmitter/receiver 7. The radio frequency transmitter/receiver 7 amplifies the received modulated FM signal and sends to the base station from the antenna 8.
When the radio frequency FM signal are received from the base station via the antenna 8, the radio frequency transmitter/receiver 7 sends the radio frequency FM signal to the FM modulation/demodulation portion 10. The FM modulation/demodulation portion 10 demodulates the radio frequency FM signal and outputs the demodulated signal to the analog voice signal processing portion 12. The analog voice signal processing portion 12 demodulates the demodulated signal to form the analog voice signal and sends it to the speaker 2. The speaker 2 converts the analog voice signal to voice output.
The control portion 11 controls the devices in the radio communication apparatus and changes the control between digital communications and analog communications.
As the conventional radio communication apparatus is constructed as explained above, the signal goes through the linear codec 3 and DSP 4 during digital communications, and it goes through the analog voice signal processing portion 12 during analog communications. That is, since the voice processing portion for digital and analog communications are provided separately, the circuit configuration becomes large and also expensive.
It is a primary object of the present invention to provide a radio communication apparatus having a small size voice processing portion and thereby to provide an inexpensive and light weight radio communication apparatus.